Computer scientists and mathematicians often vocalize it as star (as, for example, in the A* search algorithm or C*-algebra). In English, an asterisk is usually five-pointed in sans-seriftypefaces, six-pointed in serif typefaces,[citation needed] and six- or eight-pointed when handwritten. It is often used to censor offensive words, and on the Internet, to indicate a correction to a previous message.

The asterisk derives from the two thousand year old character used by Aristarchus of Samothrace called the asteriskos, ※, which he used when proofreading Homeric poetry to mark lines that were duplicated.[3]Origen is known to have also used the asteriskos to mark missing Hebrew lines from his Hexapla.[4] The asterisk evolved in shape over time, but its meaning as a symbol used to correct defects remained.

In the Middle Ages, the asterisk was used to emphasize a particular part of text, often linking those parts of the text to a marginal comment.[5] However, an asterisk was not always used.

One hypothesis to the origin of the asterisk is that it stems from the five thousand year old Sumerian character dingir, 𒀭,[6] though this hypothesis seems to only be based on visual appearance.[7]

When toning down expletives, asterisks are often used to replace letters. For example, the word 'fuck' might become 'f**k', 'f*ck' or even '****'.[8] Vowels tend to be censored with an asterisk more than consonants, but the intelligibility of censored profanities with multiple syllables such as b*ll*cks (bollocks) or uncommon ones is higher if put in context with surrounding text.[9]

The usage of the term in sports arose after the 1961 baseball season in which Roger Maris of the New York Yankees broke Babe Ruth's 34-year-old single-season home run record. Because Ruth had amassed 60 home runs in a season with only 154 games, compared to Maris's 61 over 162 games, baseball commissioner Ford Frick announced that Maris's accomplishment would be recorded in the record books with an explanation (often referred to as "an asterisk" in the retelling). In fact, Major League Baseball had no official record book at the time, but the stigma remained with Maris for many years, and the concept of a real or figurative asterisk denoting less-than-official records has become widely used in sports and other competitive endeavors. A 2001 TV movie about Maris's record-breaking season was called 61* (pronounced sixty-one asterisk) in reference to the controversy.

The controversy over season length in relation to home run records had somewhat subsided by the time Hank Aaron broke Ruth's career home run record in 1974 (although Aaron received an even larger volume of hate mail and death threats which in his case often focused on race). Maris's single season mark was broken in 1998 by Mark McGwire and Sammy Sosa, who both broke it in under 154 games. McGwire's record of 70 home runs was later eclipsed by Barry Bonds, who set the current mark of 73 home runs in the 2001 season. However, these players' accomplishments were soon questioned after evidence surfaced suggesting all three might have been taking advantage of MLB's then-lax policies related to the use of performance-enhancing drugs.

Fans were especially critical of Bonds and invoked the asterisk notion during the 2007 season, as he approached and later broke Hank Aaron's career home run record.[11] Opposing fans would often hold up signs bearing asterisks whenever Bonds came up to bat. After Bonds hit his record-breaking 756th home run on August 7, 2007, fashion designer and entrepreneur Marc Ecko purchased the home run ball from the fan who caught it, and ran a poll on his website to determine its fate. On September 26, Ecko revealed on NBC's Today show that the ball will be branded with an asterisk and donated to the Baseball Hall of Fame. The ball, marked with a die-cut asterisk, was finally delivered to the hall on July 2, 2008 after Marc Ecko unconditionally donated the artifact rather than loaning it to the hall as originally intended.

In recent years, the asterisk has come into use on baseball scorecards to denote a "great defensive play."[12]

By the end of the first decade of the 21st century, the association of baseball and its records with doping had become so notorious that the term "asterisk" had become firmly associated with doping in sport. In February 2011 the United States Olympic Committee and the Ad Council launched an anti-steroid campaign called "Play Asterisk Free"[13] aimed at teens. The campaign, whose logo uses a heavy asterisk, first launched in 2008 under the name Don't Be An Asterisk.[14]

In some command line interfaces, such as the Unix shell and Microsoft's CMD, the asterisk is the wildcard character and stands for any string of characters. This is also known as a wildcard symbol. A common use of the wildcard is in searching for files on a computer. For instance, if a user wished to find a document called Document 1, search terms such as Doc* and D*ment* would return this file. Document* would also return any file that begins with Document.

In some graphical user interfaces an asterisk is pre- or appended to the current working document name shown in a window's title bar to indicate that unsaved changes exist. In many computing and Internet applications an asterisk, or another character, is displayed to indicate that a character of a password or other confidential information has been entered, without the risk of displaying the actual character.

In Commodore (and related) filesystems, an asterisk appearing next to a filename in a directory listing denotes an improperly closed file, commonly called a "splat file."

Chat Room etiquette calls on one asterisk to correct a misspelled word that has already been submitted. For example, one could post lck, then follow it with *luck or luck* (the placement of the * on the left or right is a matter of personal style) to correct the word's spelling, or if it's someone else that notices the mistake, they might also use *luck or luck*.[15]

Enclosing a phrase between two asterisks is used to denote an action the user is "performing", e.g. *pulls out a paper*, although this usage is also common on forums, and less so on most chat rooms due to /me or similar commands. Hyphens (-action-) and double colons (::action::) as well as the operator /me are also used for similar purposes.

Some international models of adding machines and printing calculators use the asterisk to denote the total, or the terminal sum or difference of an addition or subtraction sequence, respectively, sometimes on the keyboard where the total key is marked with an asterisk and sometimes a capital T, and on the printout.

In the programming languages Ruby and Python, * has two specific uses. First, the unary * operator applied to a list object inside a function call will expand that list into the arguments of the function call. Second, a parameter preceded by * in the parameter list for a function will result in any extra positional parameters being aggregated into a tuple (Python) or array (Ruby), and likewise a parameter preceded by ** will result in any extra keyword parameters being aggregated into a dictionary (Python) or hash (Ruby).

In IBM Job Control Language, the asterisk has various functions, including in-stream data in the DD statement, the default print stream as SYSOUT=*, and as a self-reference in place of a procedure step name to refer to the same procedure step where it appears.

In Haskell, the asterisk represents the set of well-formed, fully applied types; that is, a 0-ary kind of types.

In economics, the use of an asterisk after a letter indicating a variable such as price, output, or employment indicates that the variable is at its optimal level (that which is achieved in a perfect market situation). For instance, p* is the price level p when output y is at its corresponding optimal level of y*.

Also in international economics asterisks are commonly used to denote economic variables in a foreign country. So, for example, "p" is the price of the home good and "p*" is the price of the foreign good, etc.

Certain categories of character types in role-playing games are called splats, and the game supplements describing them are called splatbooks. This usage originated with the shorthand "*book" for this type of supplement to various World of Darkness games, such as Clanbook: Ventrue (for Vampire: The Masquerade) or Tribebook: Black Furies (for Werewolf: The Apocalypse), and this usage has spread to other games with similar character-type supplements. For example, Dungeons & Dragons Third Edition has had several lines of splatbooks: the "X & Y" series including Sword & Fist and Tome & Blood prior to the "3.5" revision, the "Complete X" series including Complete Warrior and Complete Divine, and the "Races of X" series including Races of Stone and Races of the Wild.

In many MUDs and MOOs, as well as "male", "female", and other more esoteric genders, there is a gender called "splat", which uses an asterisk to replace the letters that differ in standard English gender pronouns. For example, h* is used rather than him or her. Also, asterisks are used to signify doing an action, for example, "*action*".

In linguistics, an asterisk is placed before a word or phrase to indicate that it is not used, or there are no records of it being in use. This is used in several ways depending on what is being discussed.

In the following example, the Proto-Germanic word ainlif is a reconstructed form.

*ainlif → endleofan → eleven

A double asterisk indicates a form that would be expected according to a rule, but is not actually found. That is, it indicates a reconstructed form that is not found or used, and in place of which another form is found in actual usage:

For the plural, **kubar would be expected, but separate masculine plural akābir أكابر and feminine plural kubrayāt كبريات are found as irregular forms.

In most areas of linguistics, but especially in syntax, an asterisk in front of a word or phrase indicates that the word or phrase is not used because it is ungrammatical.

wake her up / *wake up her

An asterisk before a parenthesis indicates that the lack of the word or phrase inside is ungrammatical, while an asterisk after the opening bracket of the parenthesis indicates that the existence of the word or phrase inside is ungrammatical.

Since a word marked with an asterisk could mean either "unattested" or "impossible", it is important in some contexts to distinguish these meanings. In general, authors retain asterisks for "unattested", and prefix ˣ, **, †, or a superscript "?" for the latter meaning.[citation needed] An alternative is to append the asterisk (or another symbol, possibly to differentiate between even more cases) at the end.[citation needed]

In the early days of the International Phonetic Alphabet, an asterisk was sometimes used to denote that the word it preceded was a proper noun.[19] See this example from W. Perrett's 1921 transcription of Gottfried Keller's "Das Fähnlein der sieben Aufrechten":[20]

In fine mathematical typography, the Unicode character U+2217∗ASTERISK OPERATOR (in HTML, &lowast;) is available. This character also appeared in the position of the regular asterisk in the PostScript symbol character set in the Symbol font included with Windows and Macintosh operating systems and with many printers. It should be used in fine typography for a large asterisk that lines up with the other mathematical operators.

In the Geneva Bible and the King James Bible, an asterisk is used to indicate a marginal comment or scripture reference.

In the Leeser Bible, an asterisk is used to mark off the seven subdivisions of the weekly Torah portion. It is also used to mark the few verses to be repeated by the reader of the Haftara.

In American printings of the Book of Common Prayer, an asterisk is used to divide a verse of a Psalm in two portions for responsive reading. British printings use a spaced colon (" : ") for the same purpose.

In many scientific publications, the asterisk is employed as a shorthand to denote the statistical significance of results when testing hypotheses. When the likelihood that a result occurred by chance alone is below a certain level, one or more asterisks are displayed. Popular significance levels are <0.05 (*), <0.01 (**), and <0.001 (***).

The asterisk is used to call out a footnote, especially when there is only one on the page. Less commonly, multiple asterisks are used to denote different footnotes on a page (i.e., *, **, ***). Typically, an asterisk is positioned after a word or phrase and preceding its accompanying footnote. Other characters are also used for this purpose, including †, ‡, superscript numbers (as in Wikipedia), etc. In marketing and advertising, asterisks or other symbols are used to refer readers discreetly to terms or conditions for a certain statement, the "small print".

In English-language typography the asterisk is placed after all other punctuation marks (for example, commas, colons, or periods) except for the dash.[24][25]

Three spaced asterisks centered on a page may represent a jump to a different scene, thought, or section.

Asterisks may denote corrections to misspelling or misstatements in previous electronic messages, particularly when replacement or retraction of a previous writing is not possible, such as with "immediate delivery" messages or "instant messages" that can't be edited. Usually this takes the form of a message consisting solely of the corrected text, with an asterisk placed prior to the correction. For example, one might send a message reading "*morning" to correct the misspelling in the message "I had a good mroning".